The present invention relates generally to variable optical attenuation, and more particularly, to methods and devices for MEMS-based variable optical attenuation of optical signals.
The wide application of variable optical attenuation of optical signals within optical communications networks insures that enhancements in variable optical attenuators and attenuation methods and capabilities can improve the field of optical network technology. Innovations that increase the performance qualities and lower the cost of manufacture of variable optical attenuators, or VOA""s, are also of value to communications technologists.
The prior art has attempted to improve the devices and techniques of light beam reflection by employing concave mirrors. U.S. Pat. No. 4,459,022, Morey (Jul. 10, 1984), discloses an apparatus that includes a concave mirror coupled with optical fibers. Morey""s device uses optical fibers as position detecting elements in an electrically passive detecting head. Morey discloses an embodiment wherein a concave mirror is permanently and fixedly mounted onto a movable handle. An optical fiber directs a light beam at the concave mirror, and a plurality of output optical fibers receives portions of the light beam after reflection from the concave mirror. The reflection of the light beam from the concave mirror to the output optical fiber is affected as a user moves the handle while changing the handle position. Observing the portions of the reflected light beam as transmitted through the plurality of output optical fibers are used to determine the position of the handle at the moment of reflection of the light beam from the concave mirror.
U.S. Pat. No. 6,031,946, Bergmann (Feb. 29, 2000), discloses an optical switch having two optical fibers, a concave mirror, a mirror actuator, and a mechanical actuating member attached to the mirror and to the actuator. The actuating member drives the mirror from one preset, discrete position, to another preset position, wherein each discrete mirror position provides a prespecified degree of attenuation of transmission of an optical beam from one optical fiber to another optical fiber.
There is a long felt need to improve the devices and techniques of variable optical attenuation wherein attenuation can be accomplished with more elegance and flexibility than provided in the prior art.
It is an object of the present invention to provide a variable optical attenuator, or VOA, coupled with a substrate.
It is an object of certain preferred embodiments of the present invention to provide a MEMS-based VOA.
It is another object of certain alternate preferred embodiments of the present invention to provide a variable optical attenuator, or VOA, integrated on a substrate.
It is a still alternate object of certain preferred embodiments of the present invention to provide a VOA that includes a focusing mirror.
It is yet another object of certain preferred embodiments of the present invention to provide a MEMS-based device that comprise or partially comprises a VOA.
It is still another object of certain preferred embodiments of the present invention to provide an array of MEMS-based devices that comprise or partially comprise a multi-channel MEMS-based VOA.
The method of the present invention provides a VOA for attenuating an optical signal where the optical signal is transmitted at least partially via a light beam. In a first preferred embodiment of the present invention, or an invented VOA, a movable focusing mirror of the invented VOA is positioned by an actuator to reflect, focus and steer the light beam toward a receiving photonic component. The movable focusing mirror steers and controllably misaligns the light beam onto a receiving face of the photonic device. The controlled misalignment of the light beam onto the receiving face enables an attenuation of the optical signal by allowing only a portion of the reflected light beam to enter the photonic component for transmission.
The movable focusing mirror may be a concave mirror, a diffractive mirror, a diffractive concave mirror, a Fresnel mirror, a Zone plate mirror, or another suitable movable focusing mirror known in the art.
The actuator may be or comprise, in various alternate preferred embodiments of the present invention, a suitable actuating element known in the art, to include an electro-mechanical actuator, an electro-static actuator, a piezo-electric actuator, a thermo-mechanical actuator, an electromagnetic actuator, and a polymer actuator. Where the actuator comprises a polymer actuator, the polymer actuator may be or comprise an electro-active polymer actuator, an optical-active polymer, a chemically active polymer actuator, a magneto-active polymer actuator, an acousto-active polymer actuator, a thermally active polymer actuator or another suitable polymer actuator known in the art.
A photonic component as defined herein includes mirrors, prisms, wave guides, optical fibers, lenses, collimators, and other suitable photonic and optical devices and elements known in the art. A lens as defined herein includes a suitable optical lens, spherical lens, aspherical lens, ball lens, GRIN lens, C-lens and lens system. A wave guide as defined herein includes suitable optical fibers, planar wave guides, photonic crystal wave guides, and other suitable channels for optical signal and light energy transmission known in the art.
In the invented VOA the light beam strikes the receiving photonic device as reflected, focused and steered by the movable focusing mirror upon the receiving surface of the photonic component. The movable focusing mirror, the actuator, and optionally the receiving photonic component are fabricated upon and/or with a substrate.
The pathway defined by the movement of a center of a strike circle of the light beam upon the receiving surface is a trajectory of the light beam. In various preferred embodiments of the present invention the trajectory may comprise a shape of at least one dimension or of at least two dimensions.
The movable focusing mirror, the actuator, and the receiving photonic component of the first preferred embodiment of the present invention are coupled to the substrate. In certain various preferred embodiment, the substrate may be or comprise a single substrate element or two or more mutually coupled substrate elements. The substrate elements are bonded, or adhered, or coupled in another suitable coupling technique known in the art.
In certain various preferred embodiments of the present invention the movable focusing mirror, the actuator, and the receiving photonic component of the invented VOA are integrated upon or within a substrate, and fabricated on the substrate. The substrate may be or comprise suitable substrate materials known in the art, to include semiconductor material, glass, silica, ceramic, metal, metal alloy, and polymer. The semiconductor material may be or comprise suitable semiconductor substrate materials, to include Silicon, Silicon Carbide, Gallium Arsenide, Gallium Nitride, and Indium Phosphide.
A second preferred embodiment is a MEMS-based VOA device, or MEMS VOA, having a substrate, a movable focusing mirror, an actuator, an input wave guide and an output wave guide. The MEMS VOA is, wholly or partially, integrated upon and/or within the substrate, and fabricated on the substrate and wholly or partially comprised as a MEMS. The wave guides have endfaces that are substantially planar and approximately parallel to a planar surface or element of the substrate. A transmission axis of each wave guide may approach its respective endface at an angle xcex8. The angle xcex8 is the angle formed between the vector of the transmission axis at the endface and a plane, where the plane is parallel to the planar surface of the substrate. The angle xcex8 is measured at the intersection of the transmission axis and the plane. The angle xcex8 is approximately within the range of 45 degrees to 90 degrees, or more optimally within a range of 75 degrees to 90 degrees.
In both the first preferred embodiment and the MEMS VOA, the actuator moves the mirror in an analog fashion relating to a control, power or actuating signal, whereby the movable focusing mirror is positionable within a linear range of motion. The first and second preferred embodiments thereby provide better resolution of attenuation than prior art systems that offer two or more discrete, pre-set positions with a range of motion.
The preferred method of the present invention includes providing a movable focusing mirror, a light beam, and a photonic component. The light beam strikes the movable focusing mirror. The movable focusing mirror reflects, focuses and steers the light beam to strike the photonic component. The mirror controllably forms a trajectory on the photonic component by moving and thereby steering the light beam to move across the photonic component. The position of the mirror thereby determines the portion of the light beam absorbed by the photonic component.
Certain alternate preferred embodiments of the method of the present invention further provide a multi-channel VOA array having a plurality of MEMS-based VOA""s fabricated on a common substrate, where each MEMS-based VOA includes a movable focusing mirror. The array accepts a plurality of optical signal inputs via a plurality of input optical fibers and positions the focusing mirror to steer each optical signal received towards or away from at least one output optical fiber.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments. Other objects, features, and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description which follows below. The invention will now be elucidated in more detail with reference to certain non-limitative examples of embodiment shown in the attached drawing figures.